Lifting General Relativity to Observer Space

• Published in: arXiv.org
• Main Authors: Gielen, Steffen, Wise, Derek K
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 04.05.2013
• Subjects: Einstein equations; Integral calculus; Mathematical analysis; Mathematics - Differential Geometry; Physics - General Relativity and Quantum Cosmology; Physics - High Energy Physics - Theory; Relativity; Spacetime; Theory of relativity
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1210.0019

The `observer space' of a Lorentzian spacetime is the space of future-timelike unit tangent vectors. Using Cartan geometry, we first study the structure a given spacetime induces on its observer space, then use this to define abstract observer space geometries for which no underlying spacetime is assumed. We propose taking observer space as fundamental in general relativity, and prove integrability conditions under which spacetime can be reconstructed as a quotient of observer space. Additional field equations on observer space then descend to Einstein's equations on the reconstructed spacetime. We also consider the case where no such reconstruction is possible, and spacetime becomes an observer-dependent, relative concept. Finally, we discuss applications of observer space, including a geometric link between covariant and canonical approaches to gravity.